Airhammer

ABSTRACT

The hammer barrel has a reciprocable power piston driven on both its power and return strokes by live air under the control of a rapid action kick valve. The piston drives a tappet which, in turn, drives a moil. The moil is held yieldably in extended position by the live air. The tappet cooperates with ducts in the barrel and thereby controls venting of the air to cause reciprocation of the piston by live air when the moil is retracted and to air lock the piston when the moil is fully extended. A supplemental cutoff valve is arranged in the barrel and is controlled by the tappet to cut off completely the air supply to the barrel, when the hammer is idle, so as to reduce the loss of pressure air and to improve starting characteristics. An air supply connection is arranged on the rear end of the barrel and is free from overhang laterally beyond the sides of the barrel. Accumulator ducts in the barrel store air compressed by the piston and employ it to assist in starting the piston from rest upon each reversal of stroke.

United States Patent [72] Inventor Samuel D. Gunning Cleveland, Ohio [21] Appl. No. 10,826 [22] Filed Feb. 12, 1970 [45] Patented Dec. 7, 1971 [73] Assignee Kent Air Tool Co.

Kent, Ohio [54] AIRHAMMER 10 Claims, 17 Drawing Figs.

[52] U.S. Cl 173/15, 91/5,173/133,173/135 [51] Int. Cl 825d 9/16 [50] Field otSearch 173/15l7; 91/5 [56] References Cited UNITED STATES PATENTS 1,453,252 4/1923 Rorive 173/16 1,703,840 2/1929 Maxson 91/5 3,305,953 173/15 X 2/1967 Von Mehren et al Primary Exa minerErnest R. Purser Attorney-John Harrow Leonard ABSTRACT: The hammer barrel has a reciprocable power piston driven on both its power and return strokes by live air under the control of a rapid action kick valve. The piston drives a tappet which, in turn, drives a moil. The moil is held yieldably in extended position by the live air. The tappet cooperates with ducts in the barrel and thereby controls venting of the air to cause reciprocation of the piston by live air when the moil is retracted and to air lock the piston when the moil is fully extended.

A supplemental cutofi valve is arranged in the barrel and is controlled by the tappet to cut off completely the air supply to the barrel, when the hammer is idle, so as to reduce the loss of pressure air and to improve starting characteristics.

An air supply connection is arranged on the rear end of the barrel and is free from overhang laterally beyond the sides of the barrel. Accumulator ducts in the barrel store air compressed by the piston and employ it to assist in starting the piston from rest upon each reversal of stroke.

PATENTEU on: 7 I971 3.625 295 sum 1 or 7 PATENTEDDEB mm 13525295 SHEET 2 UF 7 ATTG/P/VFY.

PATENTEU DEC 7 EM SHEET 3 OF 7 N wk m m L m \w N9 A PATENTED nEc 71971 SHEET 4 [1F 7 INVENTOR.

1 TTOKWE'K PATENTED DEC 7 B7! SHEET 8 [IF 7 PATENTEUDEB Han 3.625295 SHEET 7 0F 7 INVENTOR.

41.4 ATTORNEY.

AIRIIAMMER This invention relates to reciprocating airhammers.

Principal objects of the invention are to provide a reciprocating airhammer, preferably of the kick valve controlled type, wherein:

movement of the moil from a fully extended position to a retracted position initiates operation of the hammer which then continues uninterruptedly until such time as the moil is again permitted to move to a fully extended position, as by .withdrawal from the work; the moil is held yieldably in a fully extended position by live air continuously supplied thereto at line pressure from a source which operates the hammer; dead end air accumulator ducts accumulate air compressed by the piston, during its movement along the final portions of its stroke in opposite directions, respectively, and thereby cushion vibrations and impact stresses and recuperate the potential energy of the air so compressed by causing it to assist in initiating return movement of the piston at the end of its stroke in either direction; a supplemental cutoff valve completely stops admission of pressurized air to the hammer automatically when the moil is disengaged from the work; in one form, the moil is readily removable and replaceable through the front of the hammer; in a modified form, a novel spline connection of the moil with the moil supporting head of the hammer constrains the moil from rotation about its axis more effectively, and a specialized connecting cap and collar to facilitate connection and disconnection of the moil and hammer; and the air supply connection with the hammer is within the rearward projection of the periphery of the hammer so that laterally overhanging parts which would be likely to be damaged by a breakthrough of the tool are eliminated.

Various specific objects and advantages of the invention will become apparent from the following description, wherein reference is made to the drawings, in which:

FIG. 1 is a top plan view of a hammer embodying the principles of the present invention;

FIG. 2 is a longitudinal sectional view of the hammer and is taken on the line 22 in FIG. 1;

FIG. 3 is a vertical sectional view and is taken on the line 33 in FIGS. 1 and 2;

FIG. 4 is a left end view of the barrel of the hammer with the inlet head and internal fittings removed, showing the relation of the various ducts in the barrel;

FIG. 5 is a cross-sectional view of the structure illustrated in FIG. 4 and is taken on the line 55 of FIG. 4;

FIGS. 6 through are fragmentary longitudinal sectional views of the structure illustrated in FIG. 4, and are taken on the lines 6-6, 7-7, 8-8, 9-9, and 10-10, respectively, of FIG. 4;

FIG. 11 is a cross-sectional view of the barrel structure illustrated in FIG. 5, and is taken on the line 11-11 thereof;

FIG. 12 is a cross-sectional view of the structure illustrated in FIG. 5 and is taken on the line 12- 12 thereof;

FIG. 13 is a fragmentary cross-sectional view taken on the line 13-13 of FIG. 6;

FIG. 14 is a cross-sectional view taken on the line 13-13 of FIG. 2 and showing the spline connection between the moil and moil supporting head of the hammer;

FIG. 15 is a diagrammatic longitudinal sectional view similar to FIG. 2 showing the ducts, parts, and valving of the hammer by which operation and control are effected;

FIG. 16 is a longitudinal sectional view similar to FIG. 2, illustrating a modification of the invention; and

FIG. 17 is a vertical cross-sectional view taken on the line 17-17 in FIG. 16.

Referring to the drawings, the airhammer comprises a cylinder body or barrel I secured between an inlet fitting 2 at one end and a moil supporting head 3 at the other end. The fittings and barrel are clamped together in assembled relation by a plurality of tie bolts 4 so that the fitting 2 and head 3 can be detached readily for servicing.

The barrel 1 has a power cylinder bore 5 therein into which air is admitted through a passage 6, coaxial with the bore 5, and a passage 7, both in the head 2, the axes of the passages 6 and 7 being at 90 to each other.

An articulated air inlet connection is provided for admitting air from a source into the passages 6 and 7. The connection comprises an inlet tube 8 rotatably mounted in the passage 7 in coaxial relation therewith for rotation about the common axis. The tube 8 has an axial bore 9 which is connected by a suitable connector 10 to a flexible hose or rigid conduit for supplying air to the bore 9.

The tube 8 has a plurality of transverse ports 11 disposed between its ends and in communication with the bore 9 and the passage 7 in all rotated positions of the tube 8. Suitable pressure seals 12 are provided between the tube 8 and the wall of the passage 7. With this articulated connection between the bore 5 of the barrel 1 and the source of air under pressure, the entire hammer can be swung through an angle of 360 relative to the axis of tube 8 without subjecting the external conduits, which connect the hammer to the source, to appreciable twisting stresses.

Mounted in the moil supporting head 3 is a moil or tool 15. It is desirable that the moil be readily attachable and detachable and that it be constrained from rotation about its axis relative to the barrel. Also, it must be prevented from imposing on the hammer severe vibrations and impact stresses during driving of the moil to an extended position outwardly endwise of the barrel. To accomplish these ends, the moil 15 is provided between its ends with an annular flange 16 having a plurality of longitudinal splines 17 uniformly distributed about its periphery and extending parallel to the axis of the moil and barrel. The head 3 has an internal bore 18 provided with a plurality of splines 19 complementary to the splines 17, and which cooperate with the splines 17 to slidably support and guide the moil 15 and constrain it from rotation about its axis. Preferably the flange is in the form of a double-hex nut head, its apices providing twelve splines 17 for cooperation with twelve corresponding grooves or splines in the wall of the bore In order to retain the moil and its guiding flange in the bore 18 for reciprocation axially therein to an extended position, a suitable collar 20 is provided. The collar 20 has a central passage therethrough complementary to a guiding portion on the moil and disposed forwardly from the flange 16 and fitting the guiding portion of the moil with operating clearance. The collar 20 has a forwardly facing annular shoulder 21 for securing the collar in place against the front of the moil-supporting head 3.

A suitable split sleeve clamp 22 is provided and has an intumed annular flange 23 facing toward and engageable with the shoulder 21 of the collar 20. The exterior of the forward end portion of the head 3 and the interior of the sleeve clamp 22 are complementarily threaded so that the clamp 22 can be screwed in place by hand readily while in the uncontracted condition. The clamp 22 carries a bolt 24, by which it can be drawn tightly into contracted clamping relation to the forward end portion of the head 3 after it is screwed in position to draw the collar 20 tightly against the forward end of the head 3.

Here it should be noted that the usual arrangement for detachably connecting a moil to the moil-supporting head is by means of a clamp 22 having a single thread and a head having a single thread complementary to the thread of the clamp. With such an arrangement the threads can be initially engaged only in one relatively rotated position of the head and clamp. Quite often this will be a position in which the clamping bolt, such as the bolt 24, is not readily accessible for tightening when the sleeve has been turned to final clamping position with respect to the collar 20 and head 3. In order to eliminate this disadvantage, the forward end of the head 3 is provided with a plurality of identical threads, preferably at least three in number, and the interior of the clamp 22 is provided with the same number of complementary threads so that several starting positions for screwing the clamp 22 onto the head 3 are provided. For example, with six threads the sleeve will have six instead of one initial starting position and thus the clamp 22 can be screwed to a final position with respect to the head 3 and collar 20 in which the bolt 24 is readily accessible for tightening.

The head 3 has an auxiliary valving bore 25 and an auxiliary guide bore 26. The bore 25 is connected at its forward or outer end with the bore 18 and at its inner end with bore 26. The bores 5, 18, 25 and 26 are coaxial.

The moil 15 is provided with a tappet 30 which may be integral with or separate from, the moil. The inner end 31 of the tappet 30 is disposed in the forward end of the bore for receiving the blow of the power piston. The tappet is provided with a valving piston 32 which is reciprocable in an auxiliary bore 25 in the head 3, and with a stem portion 33 which is reciprocable in the bore 26. The stem 33 assists the flange 16 in guiding the moil l5 and constraining it to axial and nonrocking movement.

The moil l5 and the tappet 30 along with its piston 32 preferably are integral for better guidance for the moil and transmission of the force of the blow to the point of the moil. However, at a sacrifice in guidance, the tappet, piston, and moil may be separate from each other or the piston may be connected only to the tappet or to the moil.

For driving the moil 15, a power piston 35 is mounted for reciprocation in the bore 5 from a retracted position, at the left end of the bore 5 in FIG. 2, to an operating or power delivering position against the .inner face 31 of the tappet, at the right-hand end of the bore 5 in FIG. 2.

Air is admitted to the bore 5 at its left end for driving the piston on its power stroke and is admitted to the right end of the bore 5 for driving the piston on the return stroke. Seated in the left end of the bore 5 is a suitable plug 36. A two-piece valve sleeve 37, having a forward portion 38 and rear portion 39 is provided and holds the plug 36 firmly in place, and, in turn, is secured in place by the inlet head 2 bearing against the outer end of the portion 39.

Air from the passage 6 is supplied to the bore 5 through an annular inlet port 40 between the adjacent ends of the plug 36 and sleeve 37. The port 40 is connected by lateral ducts 41 to longitudinally extending combined air supply and air accumulating dead end cavities 42 formed in the barrel 1. The cavities 42 are connected to the left end of the bore 5 by means of an annular groove 43 so that air can be admitted from the passage 6 through the port 40, cavities 42, and groove 43 to the bore 5 at the left end of the piston 35 when the piston 35 is spaced a short distance to the right of the inner face of the plug 36.

The cavities 42 extend a considerable distance to the right beyond the groove 43 and are of relatively large diameter. Some of the cavities 42 may be longer than the others so as to conserve space. The cavities 42 function as inlet ducts to the bore 5 and as dead end compressed air accumulators for receiving and storing air under pressure supplied by the supply from the duct 6, or occasioned by inertial forces of the piston as it returns from an extended position wherein its left end is to the right of the groove 43 to a position in which its left end passes to the left beyond the groove 43.

In order to admit air from the duct 6 to the bore 5 at the right-hand end of the bore 5, the barrel is provided with suitable ducts 44 which at their left ends communicate with the passage 6 through lateral ducts 45, and an annular port 46 in the port sleeve 37. The ducts 45 deliver air to the bore 5 through ports 47 disposed at the extreme right hand of the bore 5, adjacent the inner end of the head 3.

Upon admission of air to the ducts 45 after venting the cavities 42 and the bore 5 at the left of the piston, as is later explained, the piston 35 is driven to the left after delivery of its blow.

For proper valving and control it is desirable that the moil be urged to, and yieldably held in the, fully extended position by live air from the pressure source. For this purpose the barrel is provided with a longitudinal duct 48 which at the end adjacent the plug 36 is connected by a lateral duct 48a to a radial duct 49 and axial duct 50 in the plug 36. The duct 48 at its forward or right end is connected by a transverse duct 48b to the left end of the bore 25. This connection admits live air from the passage 6 through the duct 48 continuously to the bore 25 at the left or rear of the valving piston 32. The air fed through the duct 48 to the bore 25 continuously urges the moil 15 to the right to fully extended position and yieldably holds it in that position.

The head 3 has exhaust ducts 51 which are connected to exhaust ducts 52 in the right-hand end of the barrel 1.

The inlets of the exhaust ducts 51 are open into the bore 25 of the head 3. The moil 15 between the piston 32 and flange 16 has a reduced diameter neck portion which provides within the bore 25 an annular space 53 which is in communication with the exhaust duct 51.

The length of the valving piston 32 and position of the inlet ends of the ducts 51 are such that when the moil 15 is in a retracted position, the inlet ends of the ducts 51 are fully open, but when the moil 15 is in the extended position, the inlet ends of the ducts 51 are closed by the piston 32.

An interior annular groove 55 opens inwardly into the bore 5 at a position lengthwise of the bore 5 such that it is slightly to the right of the right end of the power piston 35 when the left end of the piston 35 is slightly to the right of the groove 43. As shown in FIGS. 6 and 7, an inlet port 56 in the form of an armate notch is provided in the wall of the barrel 1 slightly to the right of the groove 55 and leads from the bore 5 into a duct 57. The duct 57 is connected to a lateral duct 58 which, through a suitable duct 59, leads to an annular valving trough 60 in the valve port sleeve 37. To the left of the groove 55 is an inlet port 61 in the form of an arcuate notch which leads to a duct 62 in the barrel. The duct 62 is connected, in turn, to a lateral duct 63 and thereby with a duct 64 in the port sleeve 37. The duct 64 is connected with the valving trough 60. The ducts 59 and 64 communicate with the valving trough 60 at locations spaced from each other axially of the barrel.

Mounted within the sleeve 37 is an annular valve plug 66 which, through its central passage, admits air continuously from the passage to the duct 50 and through the ducts 49, 48a, 48, and 48b, to the rear of the valving piston 32. The valve plug 66 has an exterior radial flange 67 which fits within and extends radially the full depth of the valving trough 60 and is of such thickness axially of the valve as to have sealed working engagement with the bottom wall of the trough 60 and endwise clearance with respect to both ends of the trough when the flange 67 is in intermediate position lengthwise of the trough 60. The plug 66 is arranged to seat and close the port 40 and to open the port 46 when the sleeve is driven fully to the right in FIG. 2, and to open the port 40 and close the port 46 when the sleeve is driven to the left.

The air from the duct 57 is admitted into the trough 60 at the right of the flange 67 and the air from the duct 62 is admitted into the trough 60 to the left of the flange 67.

The groove 55 is connected with exhaust ducts 68 in the barrel 1. The ducts 68 extend axially of the barrel and at their forward ends connect with the interior of the bore 25, to the right of the valving piston 26, and by way of the bore 26 with the exhaust ducts 51 thereof.

The barrel also is provided with dead end air accumulator cavities 70 which at their inlets ends are connected by transverse ducts 71 to the bore 5 adjacent the rear of the head 3 so as to receive air from the bore 5 in front of the piston 35 as the piston is driven on its power stroke.

OPERATION Upon the admission of live air into the duct 6 through the duct 7, the air immediately passes through ducts 50, 49, 48a, 48, and 48b to the left or rear of the valving piston 32, moving the moil 15 to its fully extended position to the right in FIG. 2.

Assuming the port 40 is closed by the valve plug 66 and the port 46 is open, the air admitted into the passage 6 also immediately flows through the port 46, duct 44, and port 47 into the bore 5 at the extreme right end thereof. This air admission assures that the piston 35 is driven to the left, beyond the port 56 and groove 55.

As the right-hand end of the piston passes to the left of the 1 port 56, air is admitted through the port 56, ducts 57, 58 and 59 to the right hand end of the valving trough 60. Just prior to this time, the valve plug 66 was closing port 40 and preventing admission of air to the cavity 42, and the port 46 was open so as to drive the piston 35 to the left.

The air admitted to the trough 60 by opening of the port 56 by the piston 35 is effective on the flange 67 of the valve plug 66 to drive the valve plug 66 to the left, thus closing the annular port 46 so that no additional air is supplied for driving the piston to the left, and opening the annular port 40 for admitting air through the cavity 42 and groove 43 into the bore 5 for driving the piston 35 to the right.

Since at this time the groove 55 is not blocked by the piston 35, air in the bore 5 in front, or to the right, of the piston 35 is conducted through the duct 68 into the space 53 in the bore 26. Since the moil is in forward position, this air can not escape as the valving piston 32 in this position is closing the exhaust duct 51. As a result the power piston 35 is airlocked in a retracted position but with line pressure applied in the bore 5 at the left end of the piston 35, and also in the accumulator cavity 42.

Upon forcing of the moil to the left in FIG. 2, as by shoving it against the work on which it is to operate, the valving piston 32 is moved to the left, venting the space 53 through the duct 51 to the atmosphere, and, therefore, by way of the duct 68, connecting the bore 5 at the right of the power piston 35 to the atmosphere. The duct 57 also is vented through the right-hand end of the bore 5.

In this starting position of the power piston 35, upon retraction of the moil and connection of the right end of the bore 5 to atmosphere by way of the groove 55 and duct 68, the piston 35 is driven instantly to the right on its power delivery stroke. When the piston 35 moved sufliciently far to the right to deliver its stroke, the left hand end of the piston passes the port 61', thus admitting line pressure at the left of the piston 35 through the ducts 62, ducts 63 and 64 to the left hand side of the flange 66, thereby driving the valve plug 66 to the right. This closes the annular port 40 and opens the port 46 so that air again flows to the extreme right end of the bore 5 through the duct 44, and drives the piston from its extended position back toward retracted position. Thereby the cycle is repeated so long as the moil is kept pressed against the work. Since the moil is continuously pressed against the work and therefore yieldably urged continuously toward retracted position, it moves to retracted position as soon as the piston 35 has retracted from contact with the tappet end 31.

If the hammer is manipulated so that the moil is no longer in engagement with the work, air through the port 49 and duct 48 drives the tappet 30 and moil to fully extended position wherein the valving piston 32 blocks the exhaust duct 51, thereby airlocking the power piston 35. So long as the moil is in retracted position the piston continues to reciprocate due to the functioning of the kick valve plug 66 and valving piston 26.

By the time the piston 35 has moved to the right almost to the point of impact with the tappet 32, it has uncovered the port 61 which then admitted air from the left end of the bore 5 to the valve plug 66 and caused it to close the port 40 and open the port 46. The piston next uncovers the groove 55 and vents the air under pressure at the left of the piston through the groove 55, duct 68, space 53 and exhaust duct 51. Almost simultaneously live air is admitted by the duct 44 to the right end of the bore 5. Therefore, the piston 35 is returned against air initially at atmospheric pressure. As the piston 35 continues on its return stroke, it first closes the trough 55, so that air to the left of the piston 35 is no longer vented, and is compressed and driven into the accumulator and inlet ducts 42 until the left end of the piston passes the groove 43. When on the return stroke, the left end of the piston 35 passes the groove 43, the air in the extreme left of the bore 5 is trapped in the dead end portion of the bore 5 and thus provides an air cushion for bringing the piston 35 to rest on the return stroke free from severe impacts and vibrations, and for supplying potential energy in the entrapped compressed air for assisting in initiating movement of the piston on its power stroke. This movement by the stored energy of the compressed dead air is assisted by the air returned from the accumulating cavities 42 after the left end of the piston passes to the right beyond the groove 43.

it is desirable to reduce shocks pneumatically and this is accomplished on the power stroke by dead end air accumulator cavities in the barrel and which can receive air compressed in front of the piston 35, after the right-hand end of the piston 35 has passed the groove 55. The compression of this air does not interfere substantially with the stroke delivered, but the resulting potential energy of the compressed air is adequate to help initiate the return of the piston 35, at the completion of its power stroke.

It is desirable also to cushion the stresses imposed on the barrel and head 3 by the moil 15 as it reaches the end of its power stroke, especially against low resistance by the work. For this purpose a resilient elastomeric washer is provided in the bore 18 of the head 3 against the rear or inner face of the collar 20 in position to be engaged and compressed by the flange 16 of the moil 15 to absorb shocks.

It is apparent from the foregoing description that the hammer will not operate so long as the moil remains in extended position, as when it is withdrawn from the work. On the other hand, when the moil is forced against work with light pressure so as to move it to retracted position, the power piston 35 immediately becomes operative, due to the action of the kick valve 66, and delivers repeated blows on the moil tappet until the supply of air under pressure is cut off at the source or the moil is withdrawn from the workpiece so it is driven to fully extended position and air locks the piston 35.

Meanwhile, heavy impact stresses and vibrations are cushioned pneumatically by the dead end air accumulating ducts and physically by the elastomeric shock absorber washer 75 Since the moil is yieldably held in extended position by live air, it does not retract under the force of gravity when the hammer is positioned with the moil pointing upwardly. The multisplined connection between the moil flange and the head 3 makes possible a very large number of rotating adjustments of the moil to overcome difficulties encountered by wear on the point and to provide a greater resistance to cramping of the moil in the head 3 when an operator uses the moil more or less as a crowbar in breaking two portions of fractured material.

A modified form of the invention is shown in H08. 16 and 17. It embodies the basic hammer operations heretofore described and certain specific features such as the supplemental normally closed cutoff valve which automatically controls admission and cutoff of pressurized air to the hammer when the tool is idle, improves the starting characteristics of the power piston, and prevents the loss of pressurized air regardless of the stopped or idle position of the driving piston.

Referring to FIGS. 16 and 17, the barrel, indicated generally at 80, may be essentially the same as that heretofore described, except for the different means connecting the moil to the barrel, the support of the barrel for manipulation, and the inclusion of a supplemental cutoff valve, all to be described.

The barrel is provided at its front end with a moil support 81 which is in the form of a heavy sleeve fixedly connected to the front of the barrel. The sleeve has a moil accommodating bore 82, with suitable bearing sleeves 83 therein, which supports the shank of the moil 84 for reciprocation axially. That portion of the moil received in bore 82 is so shaped relative to the bore that it can be inserted tappet end foremost into the bore 82.

The support 811 has a transverse bore 85 which intersects the bore 82 and extends-entirely through the support and the surrounding sidewall of the barrel.

The moil is held in position for reciprocation in the bore 82 by means of a transverse pin 86 detachably accommodated in the bore 85 and extensions thereof in the surrounding outer wall of the barrel. The moil 84 is provided with a transverse slot or groove 87 which is elongated endwise of the moil so as to receive the midportion of the pin which thereby prevents the moil from falling out of the bore 82. A bore 85a identical with the bore 85, and parallel thereto and spaced 180 therefrom about the axis of the moil is provided so that the moil can be installed for operation in two positions rotated 180 apart about its axis.

in order to support the barrel 80 from its rear end without substantial overhanging connections, the rear end of the barrel is closed by a heavy block header 88 through which are provided two parallel bores 89. The bores 89 extend entirely from one lateral edge to and through the opposite lateral edge. Suitable bolts 90 are disposed in the bores 89, respectively, and protrude beyond the lateral edges of the header 88. One bolt is receivable at its protruding ends through suitable spaced anns A of the conventional supporting bracket or yoke on the boom which supports the bucket of a power shovel. The other bolt 90 is connected to the manipulating power cylinder, so that it can be used to position the hammer at different angles to the supporting boom.

In the modification air is-admitted into the barrel to a kick valve 91, identical in form and function with the valve 66 described, described through an air inlet fitting 92 on the block 88. The fitting 92 is preferably coaxial with the piston bore of the barrel and extends rearwardly therefrom within the rearwardly projected lateral limits of the block 88, so that connection to an air supply can be made at the rear of the barrel free from any laterally overhanging parts, rather than to one side of the barrel.

Further control of the operation of the moil is obtained by the structure now to be described.

in the modification, the moil 84 is driven by a tappet 93 which preferably is separate from the moil, but which has a valving portion 93a which functions in the same manner as the valving portion 32 of the tappet 33 heretofore described. The tappet 93 is driven by a piston 94 corresponding, in general, to the piston 35 heretofore described, and a groove 95, corresponding to the groove 55, is provided in the barrel bore.

Furthermore, the piston 35 could stop in such relation to the groove 55 that it would not start as readily as desired when the moil was forced rearwardly by pressing it against the work. Further, it sometimes happened that if pressurized air were trapped both in front and to the rear of the piston, the air would tend to center the piston 35 over the groove 55, and thus would contribute to improper starting.

It is desirable that when the hammer is idle, that the air be allowed to bleed from the rear of the piston 94 to the front of the piston 94 while leaving the piston seated in the forward position, and that the large loss of pressurized air through the slot 95, when the piston is centered thereover, be eliminated. Again, it was found that the starting of the piston 94 was improved when the air in the barrel bore at opposite ends of the piston was equalized at atmospheric pressure.

In order to equalize the air pressure, preferably at atmospheric pressure, at both ends of the piston 94 when the piston is in idle position, a supplemental stop valve is provided to cut off instantly and automatically the supply of air to the valve 91 when the tool is idle.

For this purpose the barrel is provided with a valve inlet seat 96 on which seats a nonnally closed valve plug 97. The valve plug normally is driven to seated position by the incoming air, and when once seated is held tightly against the seat 96 by the pressurized air. The plug 97 seats when the tappet approaches its fully extended position.

However, it is necessary to unseat the valve when the tappet is moved a slight distance from its extended toward its retracted position, as by pushing of the moil against the work. For this purpose, the plug 97 is mounted on a rod 98 which is slidable in a stationary guide sleeve 99 mounted in the forward wall 100 of the air inlet chamber in which the kick valve 91 is located. The piston 94 has an axial bore 101 therethrough.

The rod 98 is slidable in the bore 101 of the piston 94 and fits the bore with operating clearance so that air in the bore of the barrel in which the piston 94 is reciprocable can seep through the clearance space between the rod wall of the piston 94 bore 101 from one end of the piston 94 to the other. The other end 102 of the rod 98 engages the rear end of the tappet 93.

The rod 98 is preferably of such length that when the valve 97 is seated on the seat 96, the end 102 of the rod is spaced from the rear end of the tappet a fraction of an inch, for instance, about one-eighth inch to one-fourth inch. A suitable packing ring 103 is disposed between the stem 98 and wall of the bore in the sleeve 99.

In operation, when the hammer is idle, the normally closed valve plug 97 is seated and no pressurized air can reach the interior of the barrel. Since air can seep between the rod 98 and the wall of the bore through the piston 94, the air at the front and rear of the piston equalize and can escape by seeping past the tappet 93 and to the outside air.

Upon forcing the moil against an object by pushing on the barrel of the hammer, the moil is caused to retract, thereby moving the tappet 93 toward retracted position. As soon as it has been retracted sufficiently to engage the end 102 of the rod 98, continued forward movement of the barrel while the moil is opposed by the work, unseats the valve 97 and admits fully pressurized air freely to the kick valve 91 so that it is available instantly for operating the piston in the same manner as in the form of the invention hereinbefore described. The supplemental valve provides for turning the air supply to the hammer completely on and off automatically, thus assuring that there is no appreciable loss of air while the hammer is idle and facilitating starting when the moil is forced against the work.

Having thus described my invention, l claim:

1. In a reciprocating hammer a moil member;

a moil driving tappet member;

a body supporting the members for reciprocation to extended and retracted positions, respectively, relative to the front end of the body;

a power cylinder bore in the body coaxial with the tappet member;

a power piston reciprocable in the power cylinder bore relative to the body and to the tappet member from a retracted starting position to an extended position wherein it delivers a blow on the tappet member, and from the extended position to the starting position;

valve means for successively alternately connecting the power cylinder bore at one face of the power piston to a source of air under pressure for driving the power piston on its power stroke, and at the opposite face of the power piston for driving the power piston on its return stroke;

the body having a valving bore coaxial with the power cylinder bore;

one of said members including a valving piston which is reciprocable in the valving bore to extended and retracted positions, successively, and is connected to said one member for reciprocation in substantially fixed relation therewith;

exhaust duct means in the body and normally venting the power cylinder bore at said opposite face of the power piston to the atmosphere; and

means operatively associated with the valving piston and rendered operative thereby, when the valve piston is in its extended position, to block said venting of air by the exhaust duct means;

characterized in that:

moil-extending means are drivingly connected to one of the members and are operable pneumatically to drive the moil member to, and to yieldably hold the moil member in, extended position independently of the positions into which the body is manipulated, of the operating positions of the valve means, and of the operating positions of the piston, when the moil extending means is subjected in a predetermined manner to live air from said source; and

means are provided for connecting the moil extending means continually to said source so that the moil extending means is continually subjected to said live air in said predetermined manner.

2. The structure according to claim 1 wherein the moil-extending means includes duct means in the body continually connecting the valving bore to said source of air at the inner end face of the valving piston.

3. The structure according to claim 1 wherein the body includes a rear header in the form of a rigid block, the remainder of the airhammer is supported by said header for movement therewith in fixed relation thereto;

said rear header is disposed between two laterally spaced bucket supporting arms of a power shovel boom; and

bolt means extend through the header and detachably connect the rear header between said arms for supporting the hammer by said arms.

4. The structure according to claim 1 wherein the power cylinder bore has a dead end portion at the end opposite from the tappet member, which portion provides an air accumulating cavity in which air is entrapped and compressed by the piston after the piston enters the dead end portion;

the length of said dead end portion is such that the entrapped volume of air is compressed by the piston on its return stroke to a degree much greater than that of the source and also sufficient to prevent the piston from striking said dead end of the power cylinder bore; and

said body has a duct which leads from the valve means and has a live air inlet into said power cylinder bore spaced from the dead end thereof a distance such that it is closed by the piston prior to entry of the piston into said dead end portion.

5. The structure according to claim 4 wherein the body has an air accumulating cavity with an inlet port in communication with said power cylinder bore at a location spaced from the dead end thereof so as to be closed by the piston prior to the piston reaching the dead end of the power cylinder bore.

6. The structure according to claim 5 wherein said live air inlet and said inlet port communicate with said power cylinder bore at substantially the same location endwise thereof.

7. The structure according to claim 6 wherein the communication of said live air inlet and said inlet port with said power cylinder bore is through a common groove which opens into the power cylinder bore.

8. The structure according to claim 1 wherein the moil extending means includes a normally closed supplemental inlet cutoff valve at the end of the body opposite from the moil member and operable to admit and block the supply of live air from said source to the valve means, selectively, by movement of the cutoff valve in directions endwise of the power cylinder bore, respectively;

a rigid rod is provided which has an abutment at one end drivingly engaged with the supplemental cutoff valve which extends therefrom endwise through a bore in the piston with operating clearance, and which has a second abutment drivingly engaged with one of said members so as to hold the moil member yieldably in its said extended position;

said spaced abutments being a fixed distance apart and constraining the cutoff valve and the engaged one of said members to substantially a fixed distance apart continually; and

said body having a supplemental exhaust duct connecting the innermost end of the valving bore to the atmosphere.

9. The structure according to claim 8 wherein the tappet member, when in extended position, holds the moil member in extended position; and

said second abutment directly en ages the tappet member. 10. The structure according to c arm 9 wherein a bushing is mounted in fixed position in the body between the supplemental inlet valve and piston, in coaxial relation to the rod;

the rod, at one portion near the supplemental inlet valve, is supported and guided by the bushing in coaxial relation to the piston bore, and is so supported and guided at a portion forwardly from said one portion by the wall of the bore of the piston.

k I! I l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,625,295 Dated December 7, 1971 Inventor-( D.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 56, for "13-13" read --l4-l L--.

Col. line 56, for "piston 26" read --piston 32--.

Same line, for "bore 26" read --bore 25--.

C01. 5, line 57, for "piston 26" read --piston 32--.

C01. 5, line 59, for "tappet 32" read --tappet 30--.

Col. 5, line 70, for "ducts 42 read --cavities t2--.

Col. 7, line 251, before "described," read --heretofore--.

Same line, cancel "described" (second occurrence.)

Col. 85, line 8, cancel "9 T", first occurrence.

Signed and sealed this 12th day of September 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents *RM O USCOMM-DC suave-ps9 U 5 GOVERNMENT "RVNHNG OFFiCE i959 0*366-334 

1. In a reciprocating hammer a moil member; a moil driving tappet member; a body supporting the members for reciprocation to extended and retracted positions, respectively, relative to the front end of the body; a power cylinder bore in the body coaxial with the tappet member; a power piston reciprocable in the power cylinder bore relative to the body and to the tappet member from a retracted starting position to an extended position wherein it delivers a blow on the tappet member, and from the extended position to the starting position; valve means for successively alternately connecting the power cylinder bore at one face of the power piston to a source of air under pressure for driving the power piston on its power stroke, and at the opposite face of the power piston for driving the power piston on its return stroke; the body having a valving bore coaxial with the power cylinder bore; one of said members including a valving piston which is reciprocable in the valving bore to extended and retracted positions, successively, and is connected to said one member for reciprocation in substantially fixed relation therewith; exhaust duct means in the body and normally venting the power cylinder bore at said opposite face of the power piston to the atmosphere; and means operatively associated with the valving piston and rendered operative thereby, when the valve piston is in its extended position, to block said venting of air by the exhaust duct means; characterized in that: moil-extending means are drivingly connected to one of the members and are operable pneumatically to drive the moil member to, and to yieldably hold the moil member in, extended position independently of the positions into which the body is manipulated, of the operating positions of the valve means, and of the operating positions of the piston, when the moil extending means is subjected in a predetermined manner to live air from said source; and means are provided for connecting the moil extending means continually to said source so that the moil extending means is continually subjected to said live air in said predetermined manner.
 2. The structure according to claim 1 wherein the moil-extending means includes duct means in the body continually connecting the valving bore to said source of air at the inner end face of the valving piston.
 3. The structure according to claim 1 wherein the body includes a rear header in the form of a rigid block, the remainder of the airhammer is supported by said header for movement therewith in fixed relation thereto; said rear header is disposed between two laterally spaced bucket supporting arms of a power shovel boom; and bolt means extend through the header and detachably connect the rear header between saiD arms for supporting the hammer by said arms.
 4. The structure according to claim 1 wherein the power cylinder bore has a dead end portion at the end opposite from the tappet member, which portion provides an air accumulating cavity in which air is entrapped and compressed by the piston after the piston enters the dead end portion; the length of said dead end portion is such that the entrapped volume of air is compressed by the piston on its return stroke to a degree much greater than that of the source and also sufficient to prevent the piston from striking said dead end of the power cylinder bore; and said body has a duct which leads from the valve means and has a live air inlet into said power cylinder bore spaced from the dead end thereof a distance such that it is closed by the piston prior to entry of the piston into said dead end portion.
 5. The structure according to claim 4 wherein the body has an air accumulating cavity with an inlet port in communication with said power cylinder bore at a location spaced from the dead end thereof so as to be closed by the piston prior to the piston reaching the dead end of the power cylinder bore.
 6. The structure according to claim 5 wherein said live air inlet and said inlet port communicate with said power cylinder bore at substantially the same location endwise thereof.
 7. The structure according to claim 6 wherein the communication of said live air inlet and said inlet port with said power cylinder bore is through a common groove which opens into the power cylinder bore.
 8. The structure according to claim 1 wherein the moil extending means includes a normally closed supplemental inlet cutoff valve at the end of the body opposite from the moil member and operable to admit and block the supply of live air from said source to the valve means, selectively, by movement of the cutoff valve in directions endwise of the power cylinder bore, respectively; a rigid rod is provided which has an abutment at one end drivingly engaged with the supplemental cutoff valve, which extends therefrom endwise through a bore in the piston with operating clearance, and which has a second abutment drivingly engaged with one of said members so as to hold the moil member yieldably in its said extended position; said spaced abutments being a fixed distance apart and constraining the cutoff valve and the engaged one of said members to substantially a fixed distance apart continually; and said body having a supplemental exhaust duct connecting the innermost end of the valving bore to the atmosphere.
 9. The structure according to claim 8 wherein the tappet member, when in extended position, holds the moil member in extended position; and said second abutment directly engages the tappet member.
 10. The structure according to claim 9 wherein a bushing is mounted in fixed position in the body between the supplemental inlet valve and piston, in coaxial relation to the rod; the rod, at one portion near the supplemental inlet valve, is supported and guided by the bushing in coaxial relation to the piston bore, and is so supported and guided at a portion forwardly from said one portion by the wall of the bore of the piston. 